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Ring Gear Replacement

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  • Ring Gear Replacement

    I pulled my engine today and started tearing it down. I already knew I had starter problems because it didn't always engage, it would sometimes make that aweful gear grinding sound that makes you shiver.

    Once I got the bell housing off, I discovered 4 areas on the ring gear with obvious damage to the teeth where the starter drive gear had been grinding. The starter drive was also in pretty bad shape.

    I know you can replace a starter bendix and I saw where SI sells a new ring gear. The service manual says the ring gear is shrunk on the flywheel but I couldn't find any info on replacing it. Shrunk on tells me the ring gear would have to be heated to be installed.

    I need advice on installing a new ring gear. All advice appreciated.

    "Trying to shed my CASO ways"


  • #2
    Before installing the new gear, remove the old one. If it is only worn on one side, it may be replaced backwards and serve a long life.

    To remove it, heat it with an acetylene torch, you have to heat it without too much heat reaching the body of the flywheel. that means a hot flame, moved quickly all over the ring gear. putting it on is tricky, but it can be done the same way. It will heat quicker to put it on, because you won't be heating the body as much.


    • #3
      Just did that ab couple months ago on my Avanti. Use something to support the ring gear (not on the flywheel) heat it up, and the flywheel will "drop off" Heat the new ring gear and "drop it on" It's pretty easy, an acetylene torch is a MUST!

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      • #4
        I love this forum. Why didn't I think about flipping the ring gear over. The back side is perfect. Thanks Tom.

        Using the weight of the flywheel to help remove and reinstall the ring gear is another great idea. Thanks Jim. What did you use to support just the ring gear? I am thinking about some large nuts spaced around where the just the teeth set on the edge of the nuts.

        Thanks again
        "Trying to shed my CASO ways"



        • #5
          I've never removed a Stude flywheel ring, but have done a few dozen foreign and domestic ones. Usually quite successfully removed cold. I'd Support the flywheel securely close to the point of mayhem of chiseling, etc. For re-use Some drive off remarkably easy with an aluminum bar as a punch. If the ring gear is junk, and it did not drive off easily, I'd first hacksaw between 2 teeth to the max depth allowed by the shoulder on the flywheel. A few chisel whacks in the saw cut will split the gear. If the flywheel had a tall shoulder preventing a deep cut, drilling the largest possible hole into and slightly thru the gear will weaken it enough to be split with a chisel. Before installing the gear, I'd spend a little time looking at details like which way the tooth bevels should point (toward the parked starter gear) and adequate chamfers/radius on the flywheel and gear to prevent interference that would prevent full seating. And easing down any knicks or gouges.
          I'd set the cleaned and prepped flywheel shouder down on the bench right next to the heating area. I'd place the new gear with the tooth bevels oriented on 3 hunks of firebrick and pre-set two vicegrips to pinch the gear width from the OD. I'd heat the ring gear with an oxy rosebud held at a distance and continually moving to bring the temp up evenly. A MAPP gas torch would probably be OK, but slower. One of those 50,000 BTU ReddiHeaters might work, but would require a lot of gear manipulation. Starter gears aren't real hard, but local overheating (blue) is still not a good idea. I like to check opposite the torch with a 400F Tempil stick. When the Tempil melts, I grab the gear by the teeeth with the 2 vice grips and drop it into place. After it cools off a bit I check for areas that are not sitting up against the flywheel shoulder, and seat them tight by tapping with an aluminum or brass drift on the gear face, not the teeth. If it seated a little too easily (subjective) I might put a few drops of wicking Loctite on the diametrical joint.


          • #6
            I change ring gears all the time in my shop. What Dan Timberlake wrote is correct. What I would add is not to heat the ring in one spot; heat it evenly. Do not get it red hot, the ring gear has been heat treated and you may mess up the temper. I have put them in the oven at 475f for about half an hour but the wife made me stop using her oven. Now I hang the ring by a hook in my shop and use a propane weed/ice burner till the dirt/grease in the teeth start to smoke well. When it is hot enough I quickly grab it with gloved hands and set it on the flywheel. It still amazes me how much the ring will expand. Neal


            • #7
              Heating the gear from 70 deg to 400 deg will expand it .0198, almost .020. That will probably give you .010 clearance, enough if you don't get it cocked.

              Cooling it down to zero f will shrink it .0042, a help, but not enough to get the ring on without heating it.
              Last edited by Tom Bredehoft; 10-31-2010, 12:03 PM. Reason: Add'l information


              • #8
                Another tip: If you have a big enough freezer, put the flywheel in there a few hours before installiing the ring gear. Gives you that much more clearance.
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                • #9
                  Many years ago I used to work in an automotive engineering shop, replacing ring gears was one of my jobs, here's how we dit it.
                  1. Drill down the side if the old ring gear being careful not to cut into the flwheel. when through it should spring apart, then remove.
                  2. Clean the seat area.
                  3. Sand back to bare metal the new ring gear in four places, about an inch long is plenty.
                  4. Rest the ring gear on bricks and heat with the oxy torch evely around the new gear until the metal just starts to get that blue colour when the torch is off it.
                  5. Place it on the fly wheel making sure it has seated properly all the war round, as you can expect this has to be done rather quickly.
                  6. Leve it to cool, job done.

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                  • #10
                    Make sure you have the proper Stude starter bolts before you re-install the starter. These have a short shoulder on them to align the starter into the ring gear properly.
                    64 Champ long bed V8
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                    • #11
                      Got the correct bolts.
                      "Trying to shed my CASO ways"



                      • #12
                        Here is the shadetree way to do it, in case you dont have an acetylene torch:

                        I did this on my Ford 8N tractor, but the principle is the same, perhaps easier because I had to split the tractor in half.

                        I removed the flywheel. The ring gear was shot so I drilled it and cut it with a sawzall and tossed the gear.
                        I cleaned up the flywheel and put it in the freezer overnight.
                        I could see that I could not get the ring gear hot enough with a propane torch, so I built a bonfire in the driveway. (I live in the country) I burned a few logs down so that I had a nice bed of coals. I dropped the ring gear in and raked some coals over it and let it heat up for a while while I had some beer. I took the gear out of the fire and it dropped on the frozen flywheel and it dropped into place like butter.

                        One word of caution, other than the standard safety stuff: You have to get that ring gear seated right away as it takes only a few seconds to shrink to size on the frozen flywheel. You must work fast.


                        • #13
                          I have an acetylene torch and a rose bud tip, so I think I will go with that instead of the drive way bonfire. I will probably time something with beer.
                          "Trying to shed my CASO ways"



                          • #14
                            I'm surprised that Paul didn't use the fire to make (Damper) Bread in a pan cooked in the coals then he'd have had something to eat with his beer (smile).
                            John Clements
                            Christchurch, New Zealand